This invention relates to a centrifugal blasting machine. More particularly, this invention relates to a centrifugal blasting machine having a rotating clamping device for the workpiece.
For the blasting treatment of predominantly cubically formed workpieces, such as for example cylinder blocks, cylinder covers, gear housing, etc., rotatable clamping devices or workpiece holders are required. These devices must ensure a secure hold of the workpieces and, at the same time, make possible an all-around blasting treatment. Thus, the devices should be designed in such a universal manner, so that workpieces of different sizes and shapes can be subjected to blasting treatments without the need for time-consuming exchanging operations.
A device for the conveying of cylinder blocks or similar workpieces through a centrifugal blasting machine is disclosed in German Patent No. 2,510,827, U.S. Pat. No. 4,121,387. In the device described therein, the workpiece clamping member has a fixed relationship with respect to the axis of rotation, so that concentric rotation of the workpiece is possible only if the workpiece is of the correct dimensions.
Thus, when no adjustments are made, subsequent workpieces of different heights are rotated eccentrically and no uniform blasting treatment is guaranteed. Moreover, the eccentric holding of the workpiece has a deleterious effect on the clamping members and on the rotational drive.
The workpiece holder disclosed in this cited patent is suitably preset only for cylinder blocks, so that time- and money-consuming exchange operations are necessary for other workpieces.
A centrifugal blasting machine having a different workpiece holder is disclosed in European Patent Application No. 100,944, filed on July 22, 1983. Although in this case the support plane of the holder can be adjusted with respect to the axis of rotation, separate adjusting devices with drives are required for adjusting the support plane and the gripping or holding members. As a result, the workpiece holder can become very expensive and is susceptible to breakdown.
It is an object of the present invention to provide a centrifugal blasting machine having at least one workpiece holding device by means of which workpieces of different form and size can be tightly retained in a position which is coaxial with the axis of rotation.
It is another object of the invention to provide such a centrifugal blasting machine which is less expensive to construct and less susceptible to breakdown than hitherto known centrifugal blasting machines. In particular, it is desirable that the centrifugal blasting machine be better protected against the centrifugal blasting means.
It is yet another object of the invention that the adjustment of the workpiece holding device for a given workpiece height be done automatically, so that a fully automatic operation, without manual adjustments, should also be possible for many different workpieces.
These and other objects are accomplished by means of the workpiece holding device of the present invention which comprises a support member having a support plane, a holding member having a holding plane, the support member and the holding member being diametrically opposed to one another, a bearing for rotatably bearing the support member and the holding member, rotation drive means for rotating the support member and the holding member about an axis of rotation, and adjustment means for pivotally adjusting the distance between the support member and the holding member so that they can receive and tightly retain the workpiece. The support member and the holding member are pivotable about respective pivot axes in such manner that the support plane and the holding plane are adjusted simultaneously and are at all times parallel to each other and equidistant from the axis of rotation. The adjust means includes a pivot drive.
Further advantageous refinements of the invention are described hereinbelow.
The workpiece holding device of the present invention can be adjusted, by means of a pivot drive, to the height of the workpiece to be subjected to the blasting treatment. After insertion of the workpiece, the same pivot drive can be used to tighten the clamping members so that the workpiece is tightly retained. Thereby, for the purpose of obtaining a uniform blasting treatment, the workpiece is retained in a position which is concentric with the axis of rotation.
By means of the disclosed embodiments and the drawings, the invention is illustrated in a simplified manner in the following.